Endo, Semi-auto, Cytoskeleton (Lecture 5) Flashcards
What are lysosomes?
- like cell’s stomach
- formed by budding off golgi
- hydrolysis both internal and external stuff:
-
internal: organelles that are old and/or not functioning correctly. Termed autophagy
-external: bacteria and debris engulfed by phagocytosis - not present in plants
Where are vacuoles present?
Plants and fungi
What are vacuoles functions?
- turgor pressure for cell enlargement
- storage of nutrients
- maintain ion gradients
- digest waste products (similar to lysosomes)
- sometimes contain pigments
- some protists also have specialized vacuoles
What are semi-autonomous organelles?
- mitochondria
- chloroplasts
Although surrounded by membranes, they are not part of the endomembrane system because they do not send or receive vesicles
How are semi-autonomous organelles involved in generation and usage of bio energy?
Also, what does the mitochondria and and chloroplasts go through? What do they use/ byproducts
- both use electrochemical reactions to make energy
- both have internal membranes with extensive folding to increase the surface area of the energy producing machinery
Mitochondria - (sugars + O2) -> undergoes respiration -> (ATP + H2O)
Chloroplasts - (CO2 + H2O0 -> undergoes photosynthesis-> (sugars + O2)
Why are mitochondria and chloroplast “semi-autonomous”?
- Each have their own genome
- Have their own ribosomes
- They replicate
- They have double membranes
- They have similar sizes and shapes
About the mitochondria?
- source of all cellular respiration
- two membranes; inner one has folds called cristae
- matrix is the “cytoplasm”
About chloroplast?
- two boundary membranes + internal thylakoid membrane
- stroma is the “cytoplasm**
- stacks of thylakoid are called grana
- photosynthetic reactions occur in the thylakoid and stroma
What are the roles of plastids?
Storage and pigmentation
What are the other types of plastids we learned about? (Labs)
- chromoplast - house pigments for organ colouration
- leucoplasts - no pigments
- amyloplast - starch storage
- protein plant - protein storage
What is cytoskeleton and the types?
Filamentous protein polymers
Types:
- microtubules
- intermediate filaments
- microfilaments
What is the function of cytoskeleton?
- cell shape
- cell polarity
- cell division
- cell movement and migration
- intracellular transport and cytoplasmic organization
About microtubules?
- polymer of a (alpha) / B (beta) -tublin dimers
- 13 protofilaments
- have plus and minus-ends, which gives them an inherent polarity
- switch between growing (polymerization) and shortening (depolymerization)
- must growth / shortening occurs at plus-ends
What are microtubule functions?
- cell shape and movement
- provide tracks for intercellular organelle movement
- attach to chromosomes during division to form the spindle
About microfilaments?
- polymers of actin
- two protofilaments form a helix
- also have a plus and minus-ends, which gives them an inherent polarity
- also grow by polymerization and shorten by depolymerization
- also most growth/shortening at +ends
What are the functions of microfilaments?
- cell shape and migration
- cell division
- organelle movement and cytoplasmic streaming in plants
- components of contractile elements in muscle fibres
About intermediate filaments?
- polymers of intermediate filament proteins (many types)
- varied composition depending on cell type
- do not have polarity and dynamics like MTs/MFs
- can be both inside and outside the cell
Intermediate filament functions
- structure, support, adhesion
- plants and fungi do not have intermediate filaments
Motor proteins?
- walk along cytoskeletal filaments carrying vesicles and other organelles
- bind the filament on one end, bind cargo on the other
- energy for walking comes from ATP
- walk undirectionally, either toward + or - end, depending on motor
- no motors for intermediate filaments
- no motors on prokaryotes
Motor families? Three types?
- Myosins - walk along MFs
- Kinesins - walk along MTs
- Dyneins - walk along MTs
About centrosomes (animal cell)
- microtubule-organizing centers
- this creates cell polarity, and contributes to shape
- positions many organelles
- at mitotic spindle poles to organize microtubules
- consist of two centrioles surrounded by a dense matrix of proteins
Flagella
Movements propel through watery medium (surrounded by the plasma membrane)
Cilia
Shorter than flagella, move fluids over cell surface (surrounded by the plasma membrane)
How is cilia/flagella movement by microtubules and motor proteins possible?
- dyneins cross link and slide microtubules past one another
- presence of cross links between MT causes bending
What is the structure of cilia/flagella?
- centrioles form the basal body of the cilium/flagellum, where they template and anchor the microtubules
